serial: samsung: prefer to use fifosize from driver data

If we have fifosize set in driver data we prefer to use it instead of default
fifosize value (which is always 16). If there is defined fifosize for particular
serial we prefer to use it, otherwise we use value from info, which is
common for all serials on given platform.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>